Differential pressure fluid servomotor



Jan. 18, 1949. F, K VAN ALMELO 2,459,475

DIFFERENTIAL PRESSURE FLUID SERVOMOTOR Fliled Dec. 2, 1943 4 Sheets-Sheet l I BY ,l

//2 ATTORN Jan. 18, 1949. F.` K. VAN ALMELO y2,459,475

DIFFERENTIAL PRESSURE FLUID SIERVOMOTOR Filed Dec, 2, 1945 4 sheets-sheet 2 /7/6' 5 INVENTOR 1949. F. K. VAN ALMELO DIFFERENTIAL PRESSURE FLUID SERVOMOTOR I Jan. 18,

4 SheeCS-SheeiI 3 Filed Dec. 2, 1945 Tap/vf? Jan. 18, 1949. F. K. VAN ALMELO I 2,459,475

DIFFERENTIAL PRESSURE FLUID SERVOMOTOR V Filed Deo. 2, 1943 4 Sheets-Sheet 4 /A/l/EN To@ Patented Jan. 18, 1949 UNITED STATES PATENT OFFICE DIFFERENTIAL PRESSURE FLUID SERVOMOTOR Fred K. van Almelo, Nassau, N. Y.

Application December 2, 1943, Serial No. 512,657

(c1. iai- 44) 2 Claims.

My invention relates to fluid actuated closure operators and particularly to hydraulically actuated operators for opening and closing the doors of passenger carrying vehicles such as cars, buses and the like.

For many years the brakes on commercial passenger carrying vehicles have been actuated by compressed air and, probably, because a supply of compressed air is required for the operation thereof, the door operators, likewise, have been operated by compressed air from the same source. Air brakes and door operators of the air actuated type are designed to operate at comparatively low pressures, say around one hundred pounds per square inch, and, because considerable power must be developed, have necessarily been comparatively large.

With the increasing use of hydraulic brakes which require a source of supply of liquid, usually oil, under high pressure, or upon which high pressure can be immediately developed as and when necessary, it has become desirable to provide an hydraulically operated door operator which may draw its power from the same source as the hydraulically actuated brakes, and thus avoid the necessity of providing both a source of compressed air and a source of liquid under high pressure. Furthermore, it is desirable, in many instancesto provide interlocking safety devices which prevent the doors of the passenger vehicle from being opened when the vehicle is in motion with the brakes off and the problem is considerably simplied where both the doors and brakes are actuated by the same medium. By utilizing high pressure, say of the order of one to tWo thousand pounds per square inch, a great deal of power can be generated by comparatively small mechanisms with parts moving through comparatively short distances, and thus, the size of the closure operators may be substantially reduced. Furthermore liquid under high pressure is, generally speaking, not dangerous, whereas, containers of air under high pressure may burst with explosive violence and cause serious damage.

However, due to the high pressures contemplated for use in hydraulic operators the present designs of air actuated operators are not well adapted for hydraulic operation because'of the special problems encountered in the change over involving leakages of liquid under such high pressures. Aside from the fact that leakages result in substantial loss of pressure, eiiiciency and positiveness of operation, theyare particularly objectionable in door operators employing oil as an 2` operating medium since such devices are ordinarily positioned over the doors operated thereby and through which passengers enter and leave the vehicle.

The general object of my invention is to provide an hydraulically actuated closure operator of simple, compact design Without the use of reciprocating parts, such as pistons, plungers and the like together with cranks or other linkages which are necessary to transform straight line motion into motion of rotation. Another object is to provide such a device which will withstand high liquid pressures and in which any leakage of liquid from the high pressure to the low pressure side of those parts which are directly moved by liquid pressure is returned directly to the source oi supply of the liquid. Another object is to provide an hydraulically actuated closure operator of the differential pressure type in which rotative movement is imparted to a shaft or rotor directly by liquid pressure, and in which all the motorparts rotate or oscillate rather than reciprocate. A further object is to provide a device of this character in which therate of door opening and closing may be regulated, and in which therate of opening or closing, particularly as the end of the openingjdrclosing portion of the cycle is approached, maybereduced to a desired degree to prevent slamming.

With these objects in view, my invention includes the novel elementsand the combinations and arrangements thereof described below and illustratedA in the accompanying drawings in Whichi Fig. l isa small scale'diagrammatic plan, view of my operatorshown in connection with an oper# ating valve and'l a -fragmentary pipes leading therefrom;

Fig. 2 is" operatori g i Fig. 3 is a vertical section lengthwise ofthe device and taken in aplane passing through the center of the shaf therotor and its associated parts being shown in"V elevation with portions broken awayf i f Fig. 4 is a `horizontal section of the device in the plane 4--llofli`g, 3; i

Fig. 5 is a sidee oriviewpf another species of the operatori Fig. 6 is a vertical section thereof similar to that shown in Fig, 3 and taken in a plane passing through the center ofthe shaft; the shaft or rotor and its `associated -parts'being shown in elevation with portions broken-away;

portion of the "id'e' elevation view of onev species of Fig. 1 is a section of the device in the plane 1--1 of Fia. 6;

Fig. 8 is a section of the device in the plane B- of Fig. 6

Fig. 9 is a side elevation of a third species of operator;

Fig. 10 is a vertical section of the third species of operator taken in a plane passing through the center of the shaft with certain portions broken away; the shaft or rotor and its associated parts being shown in elevation;

Fig. 11 is a section of the device in the plane II-|IofFig.10;

Fig. 12 is a fragmentary section of the device in the plane I2-I 2 of Fig. 10;

Fig. 13 is a fragmentary perspective View of the shaft or rotor in the device shown in Figs. 2, 3 and 4;

Fig. 14 is a fragmentary perspective view of the shaft or rotor in the species shown in Figs. 5, 6, '7 and 8;

Fig. 15 is a fragmentary perspective view of the shaft or rotor in the species shown in Figs. 9, 10, 11 and 12;

Fig. 16 is an enlarged fragmentary vertical section of the device showing a portion of the shaft, the packing and the packing gland; and

Figs. 1'1 and 18 are enlarged fragmentary perspective views illustrating types of packing which may be employed about the shaft.

Referring ilrstl to Figs. 2, 3 and 4, my operator comprises a body, preferably but not necessarily of laminated construction, comprising a base I provided with flanges 2 and 3 having holes il therein for the reception of bolts or screws for securing the device to a suitable foundation. Secured to the base I by means of cap screws 5 are two plate or block-like laminae 6 and 1. The top surface 8 of the base I, the bottom surface 9 of the lamina 1, and both the top and bottom surfaces of the lamina 6, are ground so that contact as nearly perfect as possible between these surfaces is attained. In addition, packing rings I3 are interposed between the base and lamina 6 and also between laminae 3 and 1,

The base is provided with ar centrally disposed cylindrical depression I2, the side wall of which forms a bearing for the lower end of the shaft or rotor I3. Preferably integral with the shaft i3 (see Fig. 13) is the outwardly extending portion Ill, the top and bottom surfaces of which are ground and are parallel and spaced apart a distance substantially equal to but just sufficiently less than the thickness of the lamina 6 to provide a running fit with the top of the base I and the bottom of the lamina 1. The periphery of the outwardly extending portion I fi is a fragmentary portion of a cylinder coaxial with the shaft I3.

The periphery of another outwardly extending portion I6 is a fragmentary portion of a larger cylinder also coaxial with the shaft I3 and is limited in extent by the parallel planes I1 and I8 which form vanes or pressure surfaces, The opening in the central portion of the lamina 6 is Shaped, as best shown in Fig. 4, to'provide vertically extending cylindrical surfaces i9, adapted to form a bearing for the shaft I3, 2i) to form a bearing for the cylindrical periphery of the portion I4, and 2l adapted to form a bearing for the cylindrical portion I6, of the rotor. It is to be understood that these cooperating bearing surfaces are ground and lapped to as small clearances as possible and yet provide a running fit between them. The angular extent of the sur- 4 faces I9, 20 and 2| are such that the shaft I3 and its associated parts may oscillate through an angle of appropriate magnitude to effect the desired movement of the closure.

In the position of the parts shown in Fig. 4, the shaft I3 is illustrated as at the limit of its clockwise movement. This, ordinarily, is the position of the parts when the door is fully open.

In communication at all times' with that portion of the space 22 which is defined in part by the surface of vane I8 is .the passage 23 which is enlarged and internally pipe threaded at the outer end '24. Communicating with this passage is a pipe 25 (see Fig. 1) which is always in communication with the source of liquid under pressure in an accumulator (not shown). A passage 26 in lamina 6 also communicates with that portion of the space 22 in block 6 which is dened in part by the surface of vane I1; communication being effected through ball check valve 21, when open, needle valve 28 and passage 29, and also through needle 3U, passage 3I, check valve 32, when open, and passage 41, Passage 26 is enlarged and threaded at its outer end 33 for the reception of pipe 311 (see Fig. 1) which communicates with valve 35. A pipe 36 provides communication between valve 35 and the sump of the accumulator (not shown), and the pipe 31 provides communication between valve 35 and pipe 2,3. The valve 35 is a two-way valve which in one position provides communication between pipes 34 and 31 and in the other position provides communication between pipes 34 and 36.

Inl order to reduce leakage along the shaft from the pressure chamber 22 in lamina v6, the shaft I3 is provided with a packing 38 below the pressure chamber and a packing 39 above the pressure chamber; the packing 39 being compressed by means of the gland 40 and the cap screws 4I.

To prevent seepage to the outside of the body of such liquid as may get past the packing 39, the shaft, above the packing, is provided with a oircumferential groove 42 which communicates with a passage 43, drilled upwardly from the bottom ofthe shaft, through the cross passage 44 (shown in end view in Fig. 3). Liquid passing downwardly through the passage `13, and also such liquid as may seep past the packing 38, collects below the bottom of the shaft in the recess I2 in the base block I and from there is drained back to the sump of the accumulator through passagesl and 46. Details of the packings will be hereinafter described.

In operation, vit is to be remembered that liquid pressure is always exerted on surface i3 of the rotor because the space 22 is always in communication with high pressure liquid in the accumulator. In the position of the parts shown in Fig. Il, the valve 35 is understood to be in that'position in which communication between pipes 34 and 36 is effected and vcommunication between pipe 31 and the valve is cut off. y

' In order to effect counter-clockwise rotatio of the shaft or rotor to close the doors, valve 35 is turned so that communication between pipes 33 and 36 is cut oif and communication is established between pipes 34 and 31. Thus, passage 23 will be placed in communication'with liquid at the accumulator pressure. v

It will be noted that the surface area of Vane i1 is substantially greater than the areaof vane i3 (because of a greater width with the same height or depth), andthe radial distances of the center ofgravity of vanes I1 and I8 from the axis of shaft i3 are so correlated that the product of the area of vane H multiplied by the radial distance `of its center of gravity from the axis .ci shaft i3 is substantially greater than the .area of vane I8 multiplied by the distance of its center of gravity from said axis. Thus, with the Vsame unit pressure on both varies a substantially greater turning moment will be exerted on shaft i3 by vane ll and the shaft will turn in a counter-clockwise direction. The liquid `under accumulator pressure in passage 26 will ilow through needle valvei and passage 3l forcing ball checkvalve 32 away from its seat, and thence into the passage 47. The liquid will .also ilow` through needle valve 28 and passage 29 into` passage` v4-'1. Thus, liquid pressure on `the surface il will move `the `rotor in a counter clockwise direction until the door is closed and surface I8 has reached the limit of its counterclockwise travel; `the liquid in passage 23 being forced back towards the accumulator. When liquid under' pressure is in passage 26 ball check valve 2'1, of course, will be held in Vclosed position.

i To open the door, the valve 35 is merely turned to the position where communication between pipes 34 and 35 is established and communication between pipes 34 and `311 is cut oil. In this position of valve 35, passage 26 is in communication with the sump ofthe accumulator and pressure on vane l1 is relieved. As soon as the pressure is relieved on vane l1, the pressure which is constantly on vane IB will turn the rotor` in `a clockwise direction. The liquid in contact with `the vane Il will be forced out of chamberil during the early part of the rotor travel both through check val-ve 21` and passages 4l and 29, `-and needle valve 28. As the surface l5 ofthe `,rotor moves clockwise across the passage communicating with check valve 21 the `ilow of liquid through this check valve will be c ut pfff and, thereafter, discharge can only be effected through passages 4l and 29 andneedle valve 2 8. `lfecause the total `effective area of the discharge passagesV is now substantially reduced the rate of clockwise movement of the rotor will be substantially` reduced and the opening movement of the door will be retarded so that it does not slam open.

`The `rate of discharge of liquid from space 22 through the .ball check valve 21 `may be regulated by turning the adjusting screw 48 Vwhich regulates the distance which the ball may move from its seat. Similarly, the rate of flow of liquid through check valve 32 may be regulated by turning adjusting screw `5l! `which controls the distance which the ball may move from its seat. The flow `through the needle valves 28 and `3l! can `be regulatedby turning the `adjusting screws 52 'and 53, respectively. Thus, the rate of .open-- ing `and closing movement and the degree of retardation may be regulated through wide ranges.`

`Jllll the passages in which the aforesaid adjusting screws are located are closed by plug screws il., all foi which may be alike, and similar to plug screw 55 which serves `to seal the opening in block 6 after passage" has been `drilled from the outside.

. In order to drain any liquid which may leak into the space 515 and also to prevent the forma# tion of a partial vacuum therein, apassage 5l maybe diilled into shaft I3 tocommunlcate with Passage 43.

.11n Figs. 5.,` 6, 7 and B I have illustrated a modiilcation ci my invention. Here, instead of having the vanes which are exposed to the liquid pres 4sure integral with the shaft ,or rotor .I3 and vpositioned wholly within one of the laminas which go to make up the body of my operator, those portions of the rotor which form .the vanes are separate elements which are `keyed to the rotor and disposed in different laminare. Thus. in this species, there is a base I which may oe substantially identical with that in the species first de scribed. On top of the base l is a block or lamina 58 within which that portion of the rotor carri/F ing the vano of smaller surface area is` enclosed. On top or the lamina V58 is a spacer plate or lamina 59 merely having a hole in the center thereof through which passes the shaft $0. On top of the lamina 59 is a plate or lamina `El which is substantially thicker than the lamina `5 8 and lwithin which is positioned that portion of the rotor having the vane of greater surface area. .On top of the lamina 5I is a cap 82, and all of the laminae are secured together by means of cap screws B3. It is to be understood that the contacting surfaces of the base, cap and intermediate laminae are ground surfaces, and that packing rings 64 are interposed between each two of these contacting elements. In the relative positions shown in Figs. 6, 7 and 8 the rotor parts are substantially in door-open position.

The laminae 58 and 6| are each formed with a central, circular passage 65 therethrough and, within the limits of laminae 58 and laminae 6l. respectively, annular blocks 6B and 6l of a circumferential length suflicient to permit the required oscillating movement oi the `rotor arcsecured by means oi lie'ys 58 and 69, respectively. Similar annular blocks (see also Fig, 14) 'Ill and 11 are secured to the shaft I3 by means of keys l2 and 13 respectively. It is to b e understood that all these 'blocks are ground to :fit closely the surfaces with which they run in Contact, and also to lit the surfaces to which they are keyed to prevent or reduce leakage therebetween.

To prevent seepage of liquid from the pressure chambers along the shaft. a packing ring 14 surrounds the shaft within the base `l, and a packing ring T5 is fitted within a groove in the shaft above lamina 6| 'This 4last mentioned ring is of larger diameter than the shaft so that it may be engaged and compressed by gland "1.6 which is secured to the cap plate 62 by means of the cap screws l1. A groove 18 is also provided in the shaft i0 above the packing ring T5 and communicates with a vertical drain 19, drilled upwardly from the bottom of the shaft, through the cross-drain 8l! which is shown in end elevation in Fig, 6.

It will be noted that the passages through laminae 58 and 6i in .the species shown in Figs. 5, 6, l and S are cylindrical, and therefore can be readily formed 'by a straight drilling or boring operation. However, in its operation, and in the means for controlling the rate thereof, it does not differ materially in construction or operation from the species shown in Figs. 2, 3 and 4. a passage Bl (see Fig. 8) `which communicates with the pressure chamber or space 82 'is always in communication with the liquid under pressure in the accumulator and hence pressure is always exerted against the vane surface 83 of the rotor and tends to move the shaft 6i! in a clockwise direction or to hold it at the limit of its movement in this direction. This, ordinarily, is the door-open position. In order to turn the rotor in i .a counter-clockwise direction to close the doorsgvalve 35 (see Fig. il is moved to the position Where pipes 34 and 31 are placed in communication. This admits liquid under accumulator pressure through pipe 34 int-o passage 84 which is enlarged and pipe-threaded at its outer end 85 to receive pipe 34. By referring particularly to Fig. 1, it will be noted that fluid under accumulator pressure in passage 84 may flow into the space 85 through the needle valve 88, ball check valve 94 and passage 81, and also through needle valve 88 and passage 89. Because the area of the vane surface 90 is greater than the area of the vane surface 83, due to the dierence in the thickness of laminas 58 and 0|, although the radial distances of the center of gravity of each vane surface from the axis of shaft 60 are the same, liquid pressure in space 85 acting on the surface of vane 90 will turn the rotor in a counter-clockwise direction. During this portion of the cycle liquid in chamber 82 will be forced back through passage 8| and the ball check valve 9| will be held closed by the fluid pressure in passage 84 and also bythe ball seating spring 92.

To open the doors or to return the rotor to the position shown in Figs. 7 and 8, it is merely necessary to turn valve 35 to the position Where communication is provided between pipes 34 and 38 and communication between pipes 34 and 31 is cut off.

With valve 35 in this position passage 84 is placed in communication with the sump and pressure in this passage and in the other spaces and passages communicating therewith is relieved. This being so, the liquid under accumulator pressure on the surface of vane 83 will now turn the rotor in a clockwise direction and force the liquid out of the space 85. In the first instance this liquid may flow into passage 84 both through the passage 89 and needle valve 88, and also through passage 93 and ball check valve 9| which is unseated by the pressure of the liquid being discharged from space 85. When a portion 1| of the rotor moves past the point where passage 93 communicates with space 85 the discharge of liquid through the ball check valve 9| stops and, thereafter, discharge takes place only through passage 88 and needle valve 88. Because the rate of liquid discharge from space 85 is substantially cut down the rate of movement of the rotor is correspondingly slowed and the doors do not slam open. The rate of passage of liquid through the needle valves can be regulated byA adjusting the screws 95 and 96 and the rate of iiow through the ball check valves 9| and 94 can be regulated by adjusting screws 91 and 98 respectively. Thus, the rate of opening and closing movement of the doors can be adjusted to meet a wide range of conditions.

The holes which are drilled for the needle valves, the ball check valves and passage 81 are sealed on the outer ends by plugs 99 all of which may be alike.

To prevent the establishment of a partial vacuum, or high pressure due to an accumulation of liquid in spaces and |0|, drains |02 and |03, respectively, communicating with the sump are provided, but passages, similar to passage 51 (see Figs. 3 and 4) communicating with passage 18, may be drilled in shaft 60.

Liquid accumulating in the base block in the space |94 at the bottom of the shaft can pass to the sump through the passages |05 and |08.

Referring to Figs. 9, l0, 11 and `12 and also to Fig. 15 I have here shown a further modification of my invention in .which the rotor is provided with two vanes or pressure surfaces of comparatively small area, one on each side of its axis of rotation, and two vanes or pressure surfaces of comparatively large area, one on each side of said axis. The portion of the rotor carrying these surfaces may be very conveniently made integral withthe shaft. Thus, in the species here illustrated, balanced pressures exist on opposite sides of the shaft at all times, and hence side thrust on the shaft, which may b-e quite high with the pressures employed is entirely eliminated.

Here, there are four laminae or plates |01, |08, |09 and |l0 superimposed on the base The base is provided withthe flanges 2 and 3 having holes therein for the reception of securing bolts and is also provided with a centrally disposed cylindrical recess the side walls of which form a bearing for the lower end of the shaft I2. Within the confines of lamina |01 there projects from opposite sides of the shaft I2 two vanes ||3 and ||4 having pressure surfaces I|5 and ||8 respectively. The lamina |01 is provided with a centrally disposed cylindrical'bore ||1 into which project two integral Ip-ortions IIB and ||9 which -bear against the shaft ||2. The lamina |01 is also provided with a passage |20 which communicates with chamber |2| between the shaft and the bore ||1 in lamina |01; The passage |20 is enlarged and internally threaded at its outer end |22 to receive the pipe 25 (see Fig. 1) The shaft l2 is also provided with a transverse passage |23 which provides communication between the chamber |2| and the chamber |24. Thus liquid pressure always exists in chambers |2| and |24 and, acting on the pressure surfaces IIB and ||5 of the vanes tends always to rotate the shaft ||2 in a clockwise direction or to hold it at the limit of its clockwise movement. To prevent a vacuum or the building up of iiuid pressure on the opposite sides of the vanes, drains |25 and |26 are provided which may communicate with the sump of the accumulator, or passages, similar to passage 51 (see Figs. 3 and 4), might be drilled in shaft I2 to provide communication with drain passage |45 in the shaft. It is to be understood that the l peripheries of the vanes ||3 and ||4 and the inside of the bore I1 have a close running t as d0 the shaft ||2 and the inside of the projections ||8 and ||9. Likewise the tops and bottoms of the vanes ||3 and ||4 have a close running fit with the bottom of lamina |08 and the top of the base respectively.

`Lamina |08 is merely a ller having a central opening therein for shaft I2 but the next above lamina |09 is substantially thicker than lamina |01 and is provided with a centrally disposed cylindrical bore |21 of the same size as bore ||1 in lamina |01. Lamina |09 is also provided with integral portions |28 and |29 similar to portions IIS and ||8, respectively, in lamina |01 and in vertical alignment therewith which bear closely against shaft ||2. Thus chambers |30 and' |3| are formed between the shaft and bore |21. Within the zone of lamina |09 the shaft is provided with oppositely disposed vanes |32 and |33 having pressure surfaces |34 and |35. In the position of the rotor shown in Fig.- 11 spaces |36 and |31 (really portions of chambers |30 and |3|) exist between the pressure surfaces |34 and |35 and the adjacent projections |28 and |29 and the shaft is provided with a. transverse passage |38 providing communication between the spaces |30 and |31. All of the laminae are firmly secured together with packing rings |39'therebetween by means of the cap screws |40. It is to be vur1de'r. tood`,`of course, `that the peripheries and the tops and bottomslof the vanes |32 and |33 have close running fltswith the surfaces which they contact. To preventdeakage downwardly along the shaft a packing ring |4| (see Fig. 10) is positioned in a groove in theshaftwithin` the base To prevent leakage upwardly along the shaft a second packing ring |42 is positioned in a groove in the `shaft within lamina H0. This last mentioned packing ring is of larger diameter than the shaft so that it is engaged by the gland `|43 and compressed thereby as the cap screws |44 are tightened. To intercept `liquid seepi'ng past the packing |42 and to prevent it from reaching the outside of thebody, the shaft H2, in a zoneabove the packing |42, is provided with an annular groove |45 which communicates with `the drain passage |46, drilled upwardly from the bottom of the shaft, through cross-drain |41 which is shown in endview in Fig. 10. the vertical passage |46 is received in the recess in the base at the bottom of the shaft and may` flow from there to the sump of the accumulator through passages |48 and |49.

Referring more particularly to Figs. 11 and 12, it will be .apparent that liquid under pressure from the accumulator is always present in passage which communicates with pipe (see Fig. 1), and that liquid pressure in chamber |2l, and `|24 which communicates with 12| through the passage I23, will always tend to` turn the rotor in a clockwise direction or to hold it at the limit of its movement in this direction.

`In order to move the rotor in a. clockwise direction, which is ordinarily the door closing movement thereof, it is merely necessary to turn valve (see Fig. 1) so that communication between pipes 34 and 36 is cut off and communication between pipes 34 and 31 is established. In this `position, liquid at accumulator pressure may flow -fl into pipe 34 which communicates with passage |50I (see Fig. 11) in lamina |09. The liquid, at accumulator pressure, in passage |50 may flow into chamber |31 through needle valve `|52 and ball check valve |53 and also through needle valve |54 and passage |55.` From chamber |31 the liquid may flow through the` transverse passage |38 in the rotor into the chamber |36. Fluid pressure built up in chambers |36 and |31 will act on vane surfaces |34 and |35 and, since these vane surfaces are larger than the vane surfaces |I5 and H6 and their centers of gravity are at the same distance from the axis of rotation as the centers of gravity of the surfaces ||5 and I6,

pressure on the vane surfaces |34 and |35 will function as a force couple and moment on the rotor which is substantially in excess of the turning moment exerted by the force couple created by the pressure on surfaces I5 and H6 but in the opposite or counter-clockwise direction. Thus the rotor will be turned in a counter-clockwise direction and the doors will be closed.

In order to open the doors it is only necessary to move valve 35 to the position wheie communication between pipes 34 and 31 is cut on and communication between pipes 34 and 36 is established. In this position passage |50 is placed in communication with the sump of the accumulator in chambers |36 and |31 is relieved. The presn sure which is constantly on vane surfaces and H6 will then move the rotor in a clockwise direction and force the liquid from chamber |36 through passage |38 into chamber |31 and thence exert a turning Liquid draining through and the pressure therein and also outwardly through passage and needle valve 54 into passage |50, and also through passage |56 and ball check valve |51 into passage |50. During this phase of the movement, check valve |53 will be held seated and check valve |51 will be forced open. However, as the rotor l l2 moves in a clockwise direction it will, as it approaches the limit of its movement in this direction, `reach the point Where communication between chamber |31 and `passage |56 is cut oir by the passage of the rotor across the entrance of passage |56 to chamber |31. When this occurs the effective cross-sectional area of the discharge passages leading from chambers |36 and |31 is substan tially reduced because, thereafter, liquid can escape only through passage |55 and needle valve |54 into passage |50.` The effect of this is to retard the clockwise movement of the rotor so that doors operated thereby will not slam open.

The rates of the opening and closing movements of the rotor may be regulated through a wide range of conditions by adjusting the needle valves and the ball check valves. Thus, the distance which ball check valve |51 can move from its seat may be varied by means of adjusting screw 16| to regulate the rate of liquid discharge from chambers |36 and |31; and the rate of liquid `iniiow into these chambers through ball check valve |53 can be similarly regulated by means of adjusting screw |62. Needle valve |52 may be adjusted by turning screw |59, and needle valve |54 may be adjusted by turning screw |60. The outer ends of the passages within which these adjusting screws are positioned are sealed by plug screws |64 all of which may be alike.

From the foregoing it will be apparent that I have provided a comparatively simple closure operator in which rotative movement of the shaft is produced directly by liquid pressure exerted on varies attachedV thereto. Thus, there are no reciprocating elements involved and all linkages such ascranks, racks and pinions, etc., which are necessary to transform reciprocating motion to rotary motion are eliminated. The principle on which the device operates affords a great deal of latitude in the manner of detailed design since the turning moment exerted on the shaft by any vane depends both upon the surface area' of the vane and also upon the distance of its center of gravity from the axis of rotation. Thus, since the pressure per unit of area on all vanes is the same, many combinations of vane size and lever arm may be employed to suit the designer. The vanes may be of the same area and different distances from the axis of rotation or of different size and the same distance from the axis of rotation. By either arrangement the necessary differential in turning moment may be attained.

In Figs. 16, 17 and 18, I have shown sections of the packing used to prevent or reduce seepage of liquid upwardly from the pressure chambers and along the shaft. Since the packings above the pressure chambers are alike in all the species I shall describe only that shown in Fig. 3. Thus, 1 is the lamina in which the packing is located, i3 is the shaft, 35 is the packing, and 46 is the gland. The shaft 3 is provided with a groove |65 in which the packing is received and the lower edge of the groove is chamfered, as shown at |66. The packing 35 is of flexible, resilient material so that it can be slipped over the shaft, and is preferably formed with an annular groove therein having the shape, in cross section, shown at |61 in Fig. 16, although it may be a mere panded by the pressure of any liquid rising around the shaft and is. forced into close contact with the top and side of the shaft groove to form a tight seal.

It is therefore to be understood that the words which I have used in describing my invention are words of description rather than of limitation, and that changes within the purview of the appended claims may be made without*l departing from the true scope and spirit of my invention.

What I claim is:

1. A iiuid motor of the differential pressure type adapted for use as a closure operator comprising a body, a shaft mounted to oscillate therein, vanes connected to said shaft and disposed in two axially spaced pairs with the vanes in each pair symmetricaly disposed with respect to the axis of said shaft to form a balanced shaft-vane assembly; said body being provided with separate chambers for each vane within which said vanes are closely tted but may oscillate with said shaft, and also with separate passages for conveying fluid under pressure to and from each of said chambers, re spectively; said passages communicating with said chambers on opposite sides of the respective vanes therein; whereby the fluid pressure on one pair of said vanes will function, as a force couple, to turn said shaft in a direction opposite the force couple created by the fluid pressure on the other pair of said vanes; the combined areas of the vanes forming one of said pairs being substantially in excess of the combined areas of the vanes forming the other of said pairs; whereby with equal unit fluid pressure on all said vanes said shaft willturn in one direction.

2. A fluid motor of the differential pressure type comprising a body, a shaft mounted to oscillate in said body, a plurality of vanes laterally projecting from opposite sides of said 'shaft within said body and arranged in at least two pairs spaced axially of said shaft to provide a balanced rotor; said body being provided with a separate annular chamber for each of said vanes and within which the vane is closely fitted but may oscillate with said shaft, and also with separate passages for the flow of fluid under pressure to and from one of the chambers within which one of each pair of vanes is fitted; said shaft having a cross bore 12 therethrough providing communication between the chambers for each pair of vanes, and said passages opening into said chambers on opposite sides of the respective vanes therein; whereby fluid under pressure entering said chambers will tend tomove said pairs of vanes in opposite direc'- tions; and the sum of the products of the surface areas of Vone pair of vanes exposed vto said fluid multiplied by the respective distances of their centers of gravity from the axis of said shaft being substantially in excess of the sum of the products of the areas of the other pair of vanes exposed to said fluidmultiplied by the respective distances of their centers of gravity from said axis; whereby, with the same fluid pressure the turning moment exerted on said shaft bysaid fluid `pressure on one of said pair of vanesr will be substantially in excess of the turning moment exerted thereby on the other pair of said vanes.

iFRED. K. VAN ALMELO.

REFERENCES CITED The followingreferences are of record in the fue of this patent:

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